Impacts of extended laboratory rearing on female fitness in Florida colonies of the parasitoid spalangia cameroni (Hymenoptera: Pteromalidae) with an analysis of wolbachia strains

Authors: MACHTINGER, E - University Of Florida; Geden, Christopher - Chris; Lovullo, Eric; Shirk, Paul

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2015
Publication Date: 11/27/2015
Citation: Machtinger, E.T., Geden, C.J., Lovullo, E.D., Shirk, P.D. 2015. Impacts of extended laboratory rearing on female fitness in Florida colonies of the parasitoid spalangia cameroni (Hymenoptera: Pteromalidae) with an analysis of wolbachia strains. Annals of the Entomological Society of America. 109(2):176-182.
DOI: https://doi.org/10.1093/aesa/sav118

Interpretive Summary: House flies and stable flies are common pests in equine and cattle facilities. Biological control is an important element in successful fly management, and parasitic wasps that attack and kill fly pupae are the most commonly used fly biocontrol agents. Commercial insectaries produce and sell the wasps to farmers and ranchers as part of growing industry to meet the demands of agricultural producers. To meet this demand, the companies must rear massive numbers of wasps over prolonged periods of time. Insect production over many years can lead to unintended changes in the populations of many species, sometimes resulting in production of an inferior product. How good is the quality of the wasps available for fly control? In this study, scientists at USDA’s Center for Medical, Agricultural and Veterinary Entomology (Gainesville, FL) and the University of Florida examined the effects of long colonization on a species of wasp that is commonly sold for fly control, Spalangia cameroni. Wasps that had been maintained in laboratory colonies for >10 years were compared to recently colonized S. cameroni. Long-colonized wasps were less effective than newly colonized wasps at finding and killing fly pupae, especially when they had to search for pupae under simulated natural conditions. The colonies were examined for Wolbachia symbionts that have been reported to affect the fitness of other insects. All of the colonies had the symbionts, and there was no evidence that the symbionts could account for changes in the quality of the parasitoids in colony. The results indicate that researchers and commercial wasp producers should start with fresh colonies every few years to ensure production of high quality insects for use in research and fly control.

Technical Abstract: Spalangia cameroni is used as a biological control agent of filth flies. These parasitoids are reared commercially, but little is known about the impact of colony age on host-seeking and life history parameters. Host-seeking in equine shavings and manure was analyzed with two colony ages established in 2000 and 2010 (144 and 24 generations in colony). These two colonies and a new 2012 colony (4 generations) were analyzed for differences in female longevity and fecundity. Wolbachia were analyzed in each colony to document strain variants. All colonies were collected from source material on the same dairy in Gilchrist County, Florida. The 2000 colony parasitized significantly fewer hosts than the 2010 colony when challenged in a complex environment. Life history parameters were significantly different between colonies, but declines were not related to colony age. Differences in reproductive productivity between the colonies could not be correlated to the presence or strain type of Wolbachia. New Wolbachia wsp and ftsZ sequences were identified in these colonies. Multiple strains of Wolbachia were found in the colonies and their presence did not vary between colony age. The invariance in strain presence showed that there was no noticeable selective pressure against Wolbachia either during colony maintenance or in the wild populations. Wolbachia sequence analysis showed that Seqvars previously recorded in different regions were present in the different colony ages suggesting these genes are not useful as geographical identifiers.